A Specific Absorption Rate (SAR) is a numerical value indicating how many electromagnetic waves radiated by a mobile terminal the human body absorbs. That is, the SAR is electromagnetic power absorbed by the human body in unit mass. Since it may cause harm to the human body when an SAR value is too high, many countries and areas stipulate an SAR limiting value. The European limiting value is 2.0 W/kg; and the America limiting value is 1.6 W/kg.
With the rapid development of the wireless communication technology, mobile terminals (such as a mobile phone and a panel personal computer, etc.) have been widely applied, and meanwhile, the impact of the electromagnetic radiation from the mobile terminal to the human health becomes a problem increasingly concerned by the public.
At present, in most SAR reduction technologies, methods such as reducing transmitter power, using wave-absorbed materials, a conductive reflector and an isolator, and coating an anti-radiation and wave-absorbing coat on an enclosure surface are adopted, but basically all these methods affect the communication signals, which does not fundamentally solve the contradiction between human body radiation security and high-quality communication.